Make Sure You Upgrade Your Camp As Soon As Possible.
This Means Lighting The Fire Day 1.
AS SOON AS POSSIBLE.
Waiting until that night, building the tents.
ASAP.
Waiting until the next night and Building the Base Camp.
There is a cooldown for roughly a day after each upgrade, so you must do each as fast as possible, to get free walls, at a level 3 camp, by the end of day 2.
Also
Dont build any walls until you get this achievement, on occasion people wont have it pop because they built their own wall on one side.
GL!